This invention relates to a device that will prevent skipping of the cover thread when forming a facing seam at high stitch rates. Skipping of the cover thread occurs when the cover thread is not on the proper side of the needle when the needle penetrates the workpiece. The invention also relates to an improved method of forming a facing seam at high stitch rates that will prevent the cover thread from skipping. The new device and method is useful in many applications including a pocket facing application.
This invention has particular application in the pocket facing operation on bluejeans. In this operation an upper layer or ply of denim is stitched, along a raw edge of the denim, to a pocket fabric ply.
In the prior art a pocket facing operation is performed by applying a modified 602 stitch that has two parallel rows of standard Type 401 stitches with a top cover thread interlaced between the two rows of Type 401 stitches. In this prior art pocket facing operation, the stitch extends straight for a short distance, then follows a radius for about 90.degree. and then extends straight for another short distance. The cover thread when properly applied is in front of the left needle and behind the right needle when the needles penetrate the fabric. The cover thread sometimes is not properly located with respect to the needle penetration points and skips one or more stitches. This problem occurs most frequently when sewing at high speeds and or when sewing a non-straight line pattern. The prior art pocket facing operation is started in the area where the stitch pattern is straight, with the right needle at the raw edge of the upper ply of material. As the stitch is formed around the radius, the cover thread sometimes skips a stitch or more, leaving the lines of Type 401 stitches unconnected and the raw edge of the upper ply of material is left uncovered by the facing stitch. As the garment is worn and washed the uncovered raw edge unravels and becomes unsightly.